Geology professor William Shilts is the executive director of the Institute of Natural Resource Sustainability at the University of Illinois.
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On June 12, the U.S. Department of Energy announced that it would restart the planning and finalize a cost estimate of the $1.5 to $1.7 billion FutureGen project, which it describes as a "first of its kind" initiative to build a near-zero emissions coal-fueled power plant. The low emissions would be achieved in part by capturing the carbon dioxide generated from the gasification of coal and "sequestering" it in geologic formations deep underground in Central Illinois, where the plant is to be located. Geology professor William Shilts, who is the executive director of the Institute of Natural Resource Sustainability at the University of Illinois, spoke to News Bureau life sciences editor Diana Yates about the state of the science of carbon sequestration.
What is the process by which carbon dioxide is sequestered underground?
There are actually three forms of geologic sequestration being studied by the Illinois State Geological Survey: 1) enhanced oil recovery, where carbon dioxide (CO2) is injected into depleted oil fields to aid in the recovery of oil left in place, 2) coal bed methane recovery, where CO2 is injected into coal seams to displace methane, which can be recovered and used, and 3) storage in deep saline formations, where the CO2 is injected into deep porous rocks. The CO2 is then trapped in pore spaces and kept in place by relatively impermeable rocks directly above. In Illinois, as well as nationally, deep saline reservoirs have the greatest storage potential.
How is a suitable site for carbon sequestration found?
Really, there are two criteria: suitable geology, and knowing you have suitable geology. In Illinois, we have suitable geology, and thanks to the work of the Illinois State Geological Survey, we know it.
The Illinois Basin, a geologic structure that underlies Illinois, southwestern Indiana, and western Kentucky, is well-suited to permanently sequester large quantities of CO2 in deep saline formations. The Mount Simon Sandstone, the target sequestration formation, is a thick layer of porous sandstone underlying much of the state. The Mount Simon is between 4,500 and 6,500 feet beneath the surface and ranges from 1,000 to 1,700 feet thick. The Eau Claire Shale is a 300- to 500-foot-thick, relatively impermeable shale that is directly above the Mount Simon and acts as a seal or caprock.
How much CO2 will be injected into the ground each year?
At the Illinois Basin - Decatur Project, funded by the U.S. Department of Energy, the ISGS is partnering with Schlumberger Carbon Services and the Archer Daniels Midland Company to sequester 1 million metric tons of CO2 over a three-year period at ADM's ethanol production facility in Decatur. When it is operational, FutureGen could sequester up to 1 million tons per year.
Has this technology been proven to work on such a large scale?
The Sleipner project in the North Sea off Norway has been injecting 1 million tons of CO2 per year since 1995. Additional large-scale projects are either under way or planned throughout the U.S. and around the world. Both FutureGen and the Illinois
Basin - Decatur Project will demonstrate sequestration at a large-scale. What we learn from these projects will be used to inform larger commercial projects as they come on line.
Can injecting liquid carbon dioxide into the ground cause earthquakes?
Earthquakes occur when pressure is released along two rock faces. The injection of CO2 is highly unlikely to cause an earthquake, unless it were to be directly injected along a fault plane. Geophysical surveys are run before injection starts to detect and avoid such faults.
Could liquid carbon dioxide migrate, escape from the ground or get into aquifers?
The Illinois Environmental Protection Agency requires that underground sources of drinking water be protected. All sequestration projects are subject to regulation under the Safe Drinking Water Act. The Mount Simon formation is more than a mile below groundwater used as a drinking source. Three major seals, or impermeable rock units, occur between the Mount Simon Sandstone and the surface throughout the Illinois Basin. These seals act as multiple barriers for the movement of CO2 once sequestered.
Do you have confidence that this technology will work?
Geologic sequestration utilizes experience from several existing industries including oil and gas production, natural gas storage, and enhanced oil recovery. For example, natural gas has been stored underground at more than 30 locations across Illinois without leakage since the 1960s. We are applying these technologies to a new purpose: storing carbon dioxide. Every effort is being made to ensure that sequestration is safe and effective, and the work we are doing now will help us answer this question.